Embodiments of the present invention relate to a depth of field maintaining apparatus, a three-dimensional (3D) display system and a display method.
Three-dimensional display has been one mainstream trend in the display field. The basic principle of the current three-dimensional display lies in: the stereoscopic vision is resulted from the parallax, i.e. a left eye of a viewer only sees a left eye image and a right eye only sees a right eye image, wherein the left eye image and the right eye image are a pair of stereoscopic images with parallax. The human brain will fuse the two images, and thus the 3D effect is produced.
A method for determining a depth of field of a displayed content by the human eyes is illustrated in FIG. 1. Two circles with a space of S at a position where a viewer is located, represent the left and right eyes of the viewer, respectively, wherein S is the pupil distance. Two squares at a position where a display screen is located represent the left and right eye images of a certain object, which are seen by the right and left eyes of the viewer, respectively. By this stereoscopic imaging, the brain of the viewer then thinks that this object is actually located at a position with a distance L from the screen plane. The distance L is the depth of field (DOF) and D is a viewing distance of the viewer. The following formula can be easily obtained according to FIG. 1.
      M    S    =      L          D      -      L      
In a current 3D display, an space between a pair of stereoscopic images on the display screen is invariable for one picture, that is to say, M is invariable. Consequently, as a position of the viewer changes, that is to say, D varies, the depth of field may changes, that is to say, and L varies as D varies. As shown in FIG. 2 (wherein a left figure shows a case before the viewing distance changes and the right figure shows a case after the viewing distance changes), S, which is the pupil distance, remains unchanged. As M is unchanged and the viewing distance of the viewer changes from D to D″, the DOF becomes from L to L″. In fact, in order to simulate more realistic picture, it is desired that the DOF is invariable.